The output window has a grey background, and uses a slightly darker grey to highlight the text of the current error. The difference between these two
greys seems too subtle to me, and I think it would be better if there were a more distinct color used for this highlight.

Suggested colors:
current error color on windows with white background:
217,217,217
last error color on windows with gray background:
180,180,180
Note: the addition of the To Do list that Tor is working on may affect
this issue and issue # 17323. These should be reexamined when To Do
List is implemented.